San Angelo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the San Angelo clear sky chart from 2005-11-06 to 2024-03-08.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	8% 4 2 4 4 2 4 4 5% 6% 59%	79109
	Night	8% 4 1 3 3 2 3 4 5% 7% 61%	80522
Transparency	Day	26% 4 9% 22% 25% 14%	78836
	Night	24% 4 9% 22% 25% 16%	80315
Seeing	Day	9% 7% 23% 31% 23% 6%	13982
	Night	9% 6% 31% 39% 14% 1	24123

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	9% 5% 2 4 3 2 2 2 3 5% 62%	2847
	11th to 20th	Day	6% 4 2 2 2 1 3 2 4 6% 66%	2950
	21st to end	Day	10% 6% 2 3 3 2 3 4 5% 6% 56%	3487
February	1st to 10th	Day	9% 5% 2 4 4 3 4 3 4 6% 58%	1900
	11th to 20th	Day	11% 6% 2 4 4 2 4 4 4 5% 56%	1849
	21st to end	Day	9% 7% 2 3 2 1 3 3 4 5% 60%	1570
March	1st to 10th	Day	11% 5% 2 4 4 2 5% 4 5% 6% 51%	1870
	11th to 20th	Day	12% 6% 2 4 3 2 3 3 4 5% 56%	1980
	21st to end	Day	8% 3 1 3 4 2 3 2 4 7% 63%	2178
April	1st to 10th	Day	8% 3 2 3 3 2 3 4 5% 7% 60%	2088
	11th to 20th	Day	9% 5% 2 4 4 2 3 3 4 6% 57%	2134
	21st to end	Day	9% 3 2 5% 3 1 3 3 4 5% 62%	2162
May	1st to 10th	Day	10% 4 2 4 4 2 4 4 5% 6% 55%	2340
	11th to 20th	Day	11% 5% 3 4 4 2 4 4 5% 7% 52%	2302
	21st to end	Day	9% 5% 2 5% 4 3 5% 5% 5% 8% 50%	2531
June	1st to 10th	Day	4 2 1 3 3 3 4 3 5% 7% 65%	2340
	11th to 20th	Day	4 2 2 3 3 3 4 4 6% 7% 64%	2340
	21st to end	Day	6% 3 2 3 3 3 4 6% 6% 9% 56%	2340
July	1st to 10th	Day	7% 3 2 5% 5% 5% 6% 7% 8% 9% 43%	2340
	11th to 20th	Day	3 1 1 2 3 3 4 5% 5% 7% 65%	2340
	21st to end	Day	3 2 2 3 4 2 5% 5% 6% 10% 60%	2524
August	1st to 10th	Day	2 1 1 2 3 2 4 4 5% 7% 70%	2149
	11th to 20th	Day	7% 4 1 4 4 3 5% 6% 7% 9% 51%	2123
	21st to end	Day	4 3 2 4 6% 3 6% 6% 7% 9% 50%	2376
September	1st to 10th	Day	9% 4 2 4 5% 3 6% 5% 5% 7% 52%	2042
	11th to 20th	Day	9% 5% 2 5% 5% 3 4 5% 6% 7% 49%	1980
	21st to end	Day	9% 3 1 4 4 3 4 4 4 5% 58%	1980
October	1st to 10th	Day	5% 3 2 4 4 1 3 3 5% 6% 63%	1980
	11th to 20th	Day	9% 3 1 3 3 2 2 3 3 4 66%	1980
	21st to end	Day	11% 3 2 4 3 1 3 2 3 3 66%	1988
November	1st to 10th	Day	10% 4 1 4 3 1 2 3 3 6% 63%	1673
	11th to 20th	Day	6% 4 2 2 3 2 3 3 4 6% 65%	1710
	21st to end	Day	10% 5% 2 4 4 2 3 3 3 6% 57%	1710
December	1st to 10th	Day	12% 5% 1 4 4 2 3 3 4 5% 57%	1710
	11th to 20th	Day	9% 5% 2 4 4 2 4 4 4 6% 56%	2161
	21st to end	Day	11% 6% 1 3 2 1 2 2 2 4 66%	3135
January	1st to 10th	Night	7% 5% 2 4 3 2 2 3 3 5% 63%	4108
	11th to 20th	Night	7% 4 1 3 3 1 2 2 3 5% 69%	4047
	21st to end	Night	11% 5% 2 4 3 2 3 2 4 7% 56%	4180
February	1st to 10th	Night	9% 5% 2 4 4 2 3 3 4 6% 59%	2280
	11th to 20th	Night	13% 4 2 4 3 2 3 3 4 6% 56%	2218
	21st to end	Night	10% 4 1 4 3 2 3 3 4 6% 59%	1884
March	1st to 10th	Night	10% 5% 1 4 4 3 4 5% 5% 6% 55%	2247
	11th to 20th	Night	12% 4 1 4 4 2 3 3 4 6% 58%	1980
	21st to end	Night	7% 3 2 3 3 1 3 3 5% 8% 62%	2178
April	1st to 10th	Night	6% 4 1 3 4 2 3 4 5% 7% 61%	1868
	11th to 20th	Night	9% 4 2 3 4 2 3 3 5% 6% 58%	1777
	21st to end	Night	8% 2 2 3 3 2 3 3 4 5% 68%	1796
May	1st to 10th	Night	6% 3 1 4 3 3 4 4 6% 7% 59%	1620
	11th to 20th	Night	9% 3 2 3 3 2 4 4 6% 10% 52%	1593
	21st to end	Night	7% 3 2 4 3 2 3 4 7% 10% 55%	1745
June	1st to 10th	Night	2 3 2 2 2 3 5% 6% 10% 63%	1620
	11th to 20th	Night	3 1 1 2 3 2 4 5% 6% 9% 66%	1620
	21st to end	Night	4 2 1 3 3 2 3 4 5% 8% 65%	1620
July	1st to 10th	Night	5% 3 2 3 3 3 5% 6% 7% 12% 51%	1620
	11th to 20th	Night	2 2 1 2 3 1 2 3 5% 8% 71%	1620
	21st to end	Night	1 2 1 2 3 2 3 4 6% 11% 65%	1790
August	1st to 10th	Night	2 1 2 4 2 3 3 6% 8% 70%	1790
	11th to 20th	Night	4 3 1 4 5% 3 5% 5% 6% 10% 54%	1778
	21st to end	Night	3 2 1 3 3 3 4 6% 6% 11% 57%	1980
September	1st to 10th	Night	6% 5% 2 4 4 3 4 5% 6% 7% 56%	1916
	11th to 20th	Night	9% 4 2 4 4 3 4 4 6% 8% 52%	1980
	21st to end	Night	7% 5% 1 4 3 2 3 3 5% 8% 59%	1980
October	1st to 10th	Night	6% 2 1 3 3 3 2 4 4 7% 66%	1980
	11th to 20th	Night	11% 3 1 2 3 2 2 3 3 3 67%	1980
	21st to end	Night	9% 4 2 3 2 2 3 3 3 4 66%	2344
November	1st to 10th	Night	9% 4 1 3 3 1 3 3 4 5% 65%	2405
	11th to 20th	Night	5% 3 1 3 3 2 3 4 5% 6% 65%	2470
	21st to end	Night	13% 4 2 3 4 2 3 4 4 5% 55%	2470
December	1st to 10th	Night	11% 4 1 3 3 1 4 3 4 6% 60%	2470
	11th to 20th	Night	9% 5% 2 4 4 2 4 4 4 7% 56%	3036
	21st to end	Night	9% 6% 1 3 3 2 3 3 4 5% 60%	4532

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	27% 3 5% 16% 28% 22%	2848
	11th to 20th	Day	21% 2 8% 17% 34% 18%	2950
	21st to end	Day	30% 3 6% 19% 30% 11%	3487
February	1st to 10th	Day	29% 3 5% 17% 24% 22%	1900
	11th to 20th	Day	31% 3 6% 21% 21% 18%	1859
	21st to end	Day	28% 3 4 13% 30% 22%	1570
March	1st to 10th	Day	34% 4 7% 15% 25% 15%	1870
	11th to 20th	Day	32% 4 6% 18% 21% 19%	1980
	21st to end	Day	23% 3 9% 23% 23% 19%	2178
April	1st to 10th	Day	25% 4 8% 19% 24% 20%	2088
	11th to 20th	Day	30% 4 7% 15% 25% 20%	2134
	21st to end	Day	26% 3 6% 20% 27% 18%	2162
May	1st to 10th	Day	29% 4 9% 17% 23% 17%	2340
	11th to 20th	Day	33% 4 10% 23% 20% 10%	2306
	21st to end	Day	32% 5% 12% 24% 21% 6%	2531
June	1st to 10th	Day	19% 5% 13% 30% 25% 7%	2340
	11th to 20th	Day	18% 6% 11% 28% 26% 10%	2340
	21st to end	Day	24% 6% 12% 25% 23% 9%	2340
July	1st to 10th	Day	33% 7% 18% 26% 12% 3	2276
	11th to 20th	Day	17% 6% 13% 32% 24% 7%	2271
	21st to end	Day	17% 5% 18% 40% 19% 1	2384
August	1st to 10th	Day	15% 4 13% 34% 30% 5%	2136
	11th to 20th	Day	28% 7% 16% 29% 16% 4	2123
	21st to end	Day	28% 7% 15% 26% 19% 5%	2376
September	1st to 10th	Day	31% 7% 10% 22% 21% 9%	2042
	11th to 20th	Day	33% 6% 11% 21% 22% 7%	1980
	21st to end	Day	27% 5% 8% 22% 24% 14%	1980
October	1st to 10th	Day	22% 4 11% 24% 26% 12%	1980
	11th to 20th	Day	23% 3 7% 17% 27% 22%	1980
	21st to end	Day	26% 3 4 17% 32% 19%	1988
November	1st to 10th	Day	25% 3 8% 24% 25% 16%	1673
	11th to 20th	Day	22% 3 9% 21% 27% 18%	1710
	21st to end	Day	31% 3 5% 18% 27% 16%	1710
December	1st to 10th	Day	31% 3 6% 20% 27% 13%	1710
	11th to 20th	Day	30% 3 9% 17% 23% 18%	2159
	21st to end	Day	25% 2 3 19% 31% 20%	3135
January	1st to 10th	Night	24% 3 3 17% 32% 20%	4108
	11th to 20th	Night	19% 2 5% 21% 29% 23%	4047
	21st to end	Night	29% 4 6% 19% 27% 15%	4180
February	1st to 10th	Night	28% 3 7% 16% 24% 22%	2280
	11th to 20th	Night	32% 3 5% 17% 22% 21%	2218
	21st to end	Night	27% 3 5% 13% 27% 24%	1884
March	1st to 10th	Night	29% 4 6% 18% 25% 17%	2247
	11th to 20th	Night	29% 4 8% 17% 20% 21%	1980
	21st to end	Night	22% 4 12% 22% 22% 19%	2178
April	1st to 10th	Night	23% 5% 8% 23% 19% 22%	1868
	11th to 20th	Night	26% 5% 9% 19% 20% 21%	1777
	21st to end	Night	20% 4 10% 23% 28% 15%	1796
May	1st to 10th	Night	23% 5% 11% 20% 24% 16%	1620
	11th to 20th	Night	27% 6% 15% 22% 22% 9%	1594
	21st to end	Night	24% 6% 17% 27% 20% 7%	1746
June	1st to 10th	Night	16% 5% 18% 32% 24% 5%	1620
	11th to 20th	Night	14% 4 14% 31% 26% 10%	1620
	21st to end	Night	16% 7% 13% 27% 27% 10%	1620
July	1st to 10th	Night	23% 7% 18% 31% 17% 3	1575
	11th to 20th	Night	12% 4 14% 31% 29% 11%	1566
	21st to end	Night	11% 5% 17% 40% 25% 2	1690
August	1st to 10th	Night	13% 4 12% 33% 32% 6%	1779
	11th to 20th	Night	25% 6% 14% 30% 20% 5%	1778
	21st to end	Night	19% 8% 18% 26% 21% 7%	1980
September	1st to 10th	Night	25% 8% 11% 24% 21% 10%	1916
	11th to 20th	Night	29% 6% 14% 22% 22% 7%	1980
	21st to end	Night	24% 4 9% 25% 22% 16%	1980
October	1st to 10th	Night	19% 4 11% 26% 23% 16%	1980
	11th to 20th	Night	24% 3 8% 17% 27% 22%	1980
	21st to end	Night	23% 3 5% 17% 28% 23%	2344
November	1st to 10th	Night	23% 3 8% 21% 25% 19%	2405
	11th to 20th	Night	21% 4 7% 21% 26% 20%	2470
	21st to end	Night	32% 3 5% 16% 27% 18%	2470
December	1st to 10th	Night	27% 2 8% 22% 25% 16%	2470
	11th to 20th	Night	30% 3 6% 18% 25% 18%	3037
	21st to end	Night	27% 3 4 17% 30% 19%	4532

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	11% 18% 32% 30% 8% 1	270
	11th to 20th	Day	13% 16% 30% 28% 11% 2	270
	21st to end	Day	10% 13% 42% 24% 8% 2	297
February	1st to 10th	Day	17% 13% 39% 23% 8%	270
	11th to 20th	Day	17% 12% 42% 23% 4 1	270
	21st to end	Day	17% 16% 44% 20% 4	225
March	1st to 10th	Day	16% 11% 41% 26% 6%	261
	11th to 20th	Day	21% 13% 35% 18% 12% 2	240
	21st to end	Day	14% 17% 39% 22% 7% 1	264
April	1st to 10th	Day	11% 13% 46% 24% 5% 1	348
	11th to 20th	Day	12% 18% 42% 23% 4	412
	21st to end	Day	11% 17% 38% 27% 6% 1	422
May	1st to 10th	Day	10% 11% 38% 33% 8% 1	603
	11th to 20th	Day	14% 7% 29% 34% 14% 3	625
	21st to end	Day	10% 6% 31% 39% 14% 1	679
June	1st to 10th	Day	5% 2 17% 47% 25% 4	630
	11th to 20th	Day	3 1 22% 45% 24% 4	630
	21st to end	Day	3 3 13% 38% 35% 7%	630
July	1st to 10th	Day	6% 3 7% 34% 38% 11%	621
	11th to 20th	Day	2 1 5% 36% 45% 11%	618
	21st to end	Day	2 4 32% 46% 15%	662
August	1st to 10th	Day	2 1 4 31% 45% 17%	447
	11th to 20th	Day	8% 1 3 31% 41% 16%	437
	21st to end	Day	4 1 6% 28% 43% 17%	495
September	1st to 10th	Day	7% 2 4 30% 37% 20%	332
	11th to 20th	Day	6% 3 7% 24% 40% 21%	270
	21st to end	Day	15% 2 6% 27% 34% 16%	270
October	1st to 10th	Day	3 3 16% 37% 34% 8%	270
	11th to 20th	Day	11% 4 27% 33% 21% 4	270
	21st to end	Day	18% 8% 27% 24% 20% 4	297
November	1st to 10th	Day	16% 4 29% 31% 17% 2	270
	11th to 20th	Day	13% 10% 26% 32% 13% 6%	270
	21st to end	Day	13% 19% 30% 22% 12% 3	270
December	1st to 10th	Day	17% 7% 26% 36% 11% 3	270
	11th to 20th	Day	8% 14% 37% 30% 10% 1	270
	21st to end	Day	18% 12% 38% 21% 11%	297
January	1st to 10th	Night	10% 6% 41% 33% 9%	950
	11th to 20th	Night	12% 8% 34% 37% 9%	903
	21st to end	Night	12% 9% 39% 34% 7%	836
February	1st to 10th	Night	14% 8% 42% 31% 6%	760
	11th to 20th	Night	15% 11% 42% 29% 3	744
	21st to end	Night	14% 13% 45% 25% 2	628
March	1st to 10th	Night	12% 11% 44% 29% 5%	747
	11th to 20th	Night	12% 10% 43% 29% 5%	540
	21st to end	Night	6% 13% 52% 26% 3	594
April	1st to 10th	Night	5% 12% 52% 28% 4	540
	11th to 20th	Night	10% 8% 54% 26% 3	533
	21st to end	Night	8% 9% 52% 27% 5%	540
May	1st to 10th	Night	6% 9% 46% 33% 4	540
	11th to 20th	Night	10% 6% 39% 35% 10%	531
	21st to end	Night	6% 4 39% 41% 10% 1	584
June	1st to 10th	Night	4 2 27% 52% 15% 1	540
	11th to 20th	Night	2 1 34% 52% 10%	540
	21st to end	Night	3 2 20% 52% 22% 1	540
July	1st to 10th	Night	6% 2 9% 49% 32% 2	525
	11th to 20th	Night	3 1 9% 57% 30% 1	522
	21st to end	Night	2 1 6% 62% 29% 1	591
August	1st to 10th	Night	1 1 9% 54% 34% 1	537
	11th to 20th	Night	4 2 8% 45% 37% 5%	534
	21st to end	Night	4 1 7% 42% 42% 4	594
September	1st to 10th	Night	5% 2 8% 45% 37% 2	540
	11th to 20th	Night	11% 1 8% 44% 34% 2	540
	21st to end	Night	10% 1 15% 46% 27% 1	540
October	1st to 10th	Night	5% 2 23% 47% 23%	540
	11th to 20th	Night	12% 4 27% 41% 15% 1	540
	21st to end	Night	11% 7% 28% 39% 14% 1	760
November	1st to 10th	Night	11% 4 28% 41% 16%	925
	11th to 20th	Night	6% 8% 31% 41% 13% 1	950
	21st to end	Night	14% 8% 34% 31% 11% 1	950
December	1st to 10th	Night	13% 7% 34% 37% 9%	950
	11th to 20th	Night	13% 9% 34% 37% 8%	950
	21st to end	Night	12% 8% 36% 38% 6%	1045

Page generated at 2024-03-05 06:24:03. Version ac07

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